Uva 10013 - Super long sums

// Accepted!

 // Header file begin
#include <iostream>
#include <cstdio>
#include <cstring>
#include <map>
#include <string>
#include <vector>
#include <cmath>
#include <cctype>
#include <sstream>
#include <set>
#include <list>
#include <stack>
#include<utility>
#include <queue>
#include <algorithm>
/// End
//..........
/// Macro
#define sf scanf
#define pf printf
#define sfint(a,b) scanf("%d %d",&a,&b)
#define sfl(a,b) scanf("%ld %ld",&a,&b)
#define sfll(a,b) scanf("%lld %lld",&a,&b)
#define sfd(a,b) scanf("%lf %lf",&a,&b)
#define sff(a,b) scanf("%f %f",&a,&b)
#define lp1(i,n) for(i=0;i<n;i++)
#define lp2(i,n) for(i=1;i<=n;i++)
#define mem(c,v) memset(c,v,sizeof(c))
#define cp(a) cout<<" "<<a<<" "<<endl
#define nl puts("")
#define sq(x) ((x)*(x))
#define all(x) x.begin(),x.end()
#define sz size()
#define gc getchar()
#define pb push_back
/// End.........

/// Size
#define mx7 20000100
#define mx6 1500000
#define mx5 100005
#define mx4 1000100
#define inf 1<<30                                           //infinity value
#define eps 1e-9
#define mx (65540)
#define mod 1000000007
#define pi acos(-1.0)

/// Macros for Graph

#define white 0
#define gray 1
#define black -1
#define nil -2

using namespace std;
//..................................................................................................................
typedef long long LL;
typedef long L;
typedef unsigned long long ull;
typedef unsigned long ul;
typedef unsigned int ui;
typedef pair<int, int> pii;

template<class T> T gcd(T a, T b ) {return b<=0?a:gcd(b,a%b);}
template<class T> T large(T a, T b ) {return a>b?a:b;}
template<class T> T small(T a, T b ) {return a<b?a:b;}
template<class T> T diffrnce(T a, T b) {return a-b<0?b-a:a-b;}

vector<int>va;
vector<int>vb;
vector<int>ans;

int main()
{
    L n,m;
    sf("%ld",&n);

    for(int k=0;k<n;k++)
    {
        if(k>0)nl;

        va.clear();
        vb.clear();
        ans.clear();

        sf("%ld",&m);

        while(m--)
        {
            int a,b;
            sf("%d",&a);
            va.push_back(a);
            sf("%d",&b);
            vb.push_back(b);
        }

        int r=0,alen=va.size();

        for(int i=alen-1;i>=0;i--)
        {
            r = va[i] + vb[i] + r;

            if(r > 9)
            {
                ans.push_back(r%10);
                r=1;
            }

            else
            {
                ans.push_back(r);
                r=0;
            }
        }

        //for(int i=0;i<ans.size();i++) cout << ans[i] << " ";
        int anslen=ans.size();

        for(int i=anslen-1;i>=0;i--)
        {
            pf("%d",ans[i]);
        }

        nl;
    }

    return 0;
}